There are many rope and cable products in the market that are used in rigging and furling applications. These conventional rope products serve as inexpensive assemblies that work sufficiently in various sailing conditions. Nevertheless, as sail boats increase in size and/or their sails become larger (e.g., larger luff length), the performance of conventional ropes becomes increasingly worse. In particular, they lack rigging/furling efficiency and safety.
A luff rope, in particular, is adapted to transmit torque up from a furler to a top swivel. Some luff ropes are described in U.S. Pat. No. 4,124,971 to Taylor et al. and U.S. Pat. No. 8,117,817 to Markham et al. For the luff rope to be effective in furling systems, numerous turns must be applied to the furler drum to “pre-twist” the luff rope and thus generate and transfer torque quickly up to the top swivel. The pre-twisting may reduce the time needed to furl a sail but may also cause an instantaneous furl at or near the top swivel. This negative outcome results in a very tight and often detrimental wrapping of the sail. In addition, the act of pre-twisting may cause the sail to overwrap about the luff rope due to the instantaneous furl. By pre-twisting the luff rope, an excess of energy is stored therein, which causes the rope to become uncontrollable when the process of furling is initiated.
Conventional luff ropes often comprise a central core of high strength material (e.g., polybenzoxazole (PBO), Kevlar®, Technora®) and multiple layers of fiber braided over the central core with adhesive disposed between the fiber layers and the core. The fiber layers may further be impregnated with resin to improve the tensile strength of each individual fiber. However, conventional ropes are not able to transmit torque efficiently and safely in furling systems (e.g., top-down furling). They have a tendency to break down with repeated use, especially when they are subjected to high tension and torque. The resin binding the fibers can fail due to the overall flexibility of the luff rope as well as fiber movement caused by core compression and rope/cable coiling. In addition, conventional ropes often form kinks when they are tightly coiled or flaked for stowage.
While conventional ropes and cables may work with furling systems, they still suffer from several disadvantages. One disadvantage is that conventional ropes fail to provide efficient torque transmission properties without relying on resin-impregnated fibers. Another disadvantage is that conventional ropes often malfunction in furling systems, either wrapping the sail too tightly or overwrapping the sail. Moreover, the ropes, and specifically their resin-impregnated fibers, are prone to break down or experience damage after repeated furling and coiling. It is therefore desired to overcome these disadvantages and provide a cable that has improved torque transmission characteristics. It is also desired to provide a cable that is robust and avoids physical breakdown and deterioration of performance associated therewith. It is further desired to provide a cable that does not require the infusion of resin into fibers in order to achieve high tensile strength and efficient torque transmission.